Compound air-compressor.



W. R. THOMPSON 6: E. E. CASE.

COMPOUND AIR COMPRESSOR.

APPLICATION IILED MAR. 16, 1910. 984,321. Patented Feb. 14, 1911.

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' UNITED STATES PATENT OFFICE.

WILLIAM R. THOMPSON AND ELMER E. CASE, OF SOUTH NORWALK, CONNECTICUT, ASSIGNORS OF ONE-HALF TO JOHN TIEBOUT. OF BROOKLYN, NEW YORK.

COMPOUND AIR-COMPRESSOR.

Specification of Letters Patent.

Patented Feb. 14, 1911.

Application filed March 16, 1910. Serial No. 549,685.

T 0 all whom it may concern:

Be 1t known that we, \VILIJA'M R. Tnoarr- SON and Emma E. Case, citizens of tho United States, residing at South Nor-walk, county of Fairfield, State oi? (.onnecticut, have invented an Improvement in Compound Air-Compressors, of which the :following is a specification.

This invention relates to air pumps or compressors ot the type in which a piston is actuated positively in one direction and in the opposite or return direction by a spring and is a carrying forward and development of the invention described and claimed in patent to W. R. Thompson, Number 910,751, dated November 23, 1909.

The present invention is adapted for general use and is especially adapted for use where a maximum of compression is required to be produced in a minimum of space, at a minimum expense and with a minimum weight and number of parts. 'With these and other objects in view we have devised the novel compound air compressor of which the following description in connection with the accompanying drawing is a specification, reference characters being used to indicate the several parts.

Figure 1 is an end elevation of our novel compressor, partly broken away; and Fig. 2 is a side elevation, partly in vertical section.

10 denotes the shaft which carries large and small cams or eccentrics, indicated respectively by 11 and 12.

13 and 14. denote respectively the large and small cylinders and 15 and 16 the large and small pistons operated by said cams l1 and 12, respectively. Said cams are preferably so ar "anged on said shaft as to cause said pistons each to make a complete rcciprocation at each complete rotation oil the shaft 10, but to cause said pistons to reach the same extreme of their movements at different times but within a period of rotation of said shaft of less than 180. To this end the cams 11 and 12 are preferably set at an angle of substantially 60 to each other. The cylinders are rigidly bolted to a body 17 in which the shaft is 'jonrnaled and which incloses the eccentrics and into which the lower ends of the pistons extend. The body may be partly filled with oil, indicated by 18, which is carried up by the eccentrics and thrown onto the lower ends of the pistons,

thus keeping the cylinders effectually lubricated.

20 denotes an oil gage attached to the body.

The pistons are shown as provided with lubricating grooves and as each provided with a head 23 which is engaged by the corresponding eccentric within the body.

21 denotes a spring which retains the head of the large piston closely .in engage meut with the corrcspoiuling cam and ell'ects the return movement of said piston. This spring bears against the head oi the large cylimler, which is indicated by 25. In order to insure the greatest possible amount of compression in the large cylinder by permitting the inner end of the piston to go practically to the end of the cylinder, we provide a circular groove 27 in the piston which receives practically the entire spring when the piston is at the extreme of its forward movement. The large cylinder is provided with an air intake, indicated by 28, having a suitable spring controlled 'alve 2!.) which opens to admit air when the piston is moving backward and closes to prevent the escape of air when the piston is moving :lorward. The large cylinder head is also provided with a lmh 30 within which is a spriug-co1itrolled valve 31 which closes to prevent the return of air when the piston is moving backward and opens to permit the passage of air from the cylinder when the piston is moving forward.

32 denotes an air pipe which is detachably connected to hub 30 and also to a hub 33 on the small cylinder head which is indicated by 26. Ilub 33 is provided with a suitable spring-contirolled valve 21 which opens to permit entrance oi. air to the small cylinder when the large piston is moving il'orward and the small piston is moving backward.

31 denotes an outlet pipe which is connectcd to a hub 35 on the small cylinder head. A suitable spring-controlled valve 30 in hub prevents entrance of air to the small cylinder when the small piston is moving backward and permits air to pass therefrom when the small cylinder is moving forward. The small piston is forced "forward by the corresponding eccentric in the same manner as the large piston, but the return movement is caused without the use 01 a spring by air entering from the large cylinder through pipe It will. thus be seen that the pistons 15 and 16 are arranged to be actuated in one direction by the cams 11 and 12 respectively, but are otherwise disconnected therefrom, the large piston being moved in the opposite direction by its spring and the small piston being moved in the opposite direction by air forced into the small cylinder by the large piston.

The operation will be obvious from the drawing. It will be noted that, by reason of the fact that the eccentrics 11 and 12 are" not opposite one another but are set at an angle of less than 180 there can be no bal ancing of the pistons and consequently it is made impossible for the shaft to become set on a dead center. During the backward movement of the large piston, air enters the large cylinder and is compressed therein during the forward movement of said piston and forced into the small cylinder through pipe the small piston being moved backward by the incoming air. Shortly after the large piston commences to move back- "ard the small piston commences to move forward and the air that has been forced into the small cylinder is further compressed therein and forced out through the outlet pipe to a suitable tank or to any point of use.

Having thus described our invention, we claim: 1

1. An improvement in air compressors comprising a body, a pair of cylinders of different diameters supported by said body and each having a closed end, an air dis charge pipe leading from the larger cylinder into the closed end of the smaller cylinder, pistons working in said cylinders, a spring acting upon the larger piston to hold the l same normally away from the closed end of its cylinder, means for periodically moving said larger piston against the pressure of said spring, whereby the air pressure created by said piston and passing from the larger cylinder to the smaller cylinder will move the smaller piston away from the closed end of its cylinder, and means for periodically moving the smaller piston in opposition to said air pressure, said moving means being arranged to move the smaller piston before the completion of the spring impelled stroke of the larger piston.

2. An improvement in air compressors comprising a body, a pair of cylinders of different diameters supported by said body and each having a closed end, an air discharge pipe leading from the larger cylinder into the closed end of the smaller cylinder, pistons working in said cylinders, a spring acting upon the larger piston to hold the same normally away from the closed end of cylinder, a shaft journaled in said body, a cam on said shaft for moving the larger piston in opposition to its spring, whereby the air pressure created by said piston and passing from the larger cylinder to the smaller cylinder will move the smaller piston away from the closed end of its cylinder, and a cam on said shaft for moving said smaller piston in opposition to said air pressure, said cams being so arranged that the smaller piston is moved in opposition to the air pressure before the completion of the spring impelled stroke of the other piston.

In testimony whereof we affix our signa tures, in presence of two witnesses.

iVILLIAM R. THOMPSON. ELMER- E. CASE. 'itnesses LEWIS ARDELL, MYnoN \V. OSBORN. 

